That was a good day right there! Winds were 12 up to 15+: maybe 20mph by landing time.
Landing: Yeah I knew better than to force it down in those winds, I let my tip drag is what did it!
Today was in testing and learning its intricacies. It's now at full (easy to get) throws.
I've still got some tweaking to do (slight CG and washout adjustments) but all in all I'm happy and I'm pretty sure that I won't need any more control throws.
It just needs to snap a slight bit more willingly. A slight CG change to the rear should do it.
My flight agenda FYI: No wags nor wobbles
"Back and forth swings/wags" whether in yaw or bank is considered an error on my part!
Turbulence caused instabilities do not count: Not my fault!
Stalled rotating maneuvers (snaps, spins) as well as hammerheads or wingovers are difficult to perform "and exit" without causing/inducing yaw and or bank instabilities. I do my best!
That Being said:
There's something about a Windfree that can't be put into words, She's floaty, light and yet slippery and fast, she's delicate, forgiving, predictable, elegant, graceful and very ballerina like in playing with accelerations and momentums. With all that there's still words missing! I've had one since the early 80's and in fact I still have my Windfree from the 80's and a video of it right here too, (If you've already watched this video there's a goto prompt in the script of my other video to shorten it). They both have their own personalities but of course also share many of the same attributes. There are not enough words to describe what you feel when flying them. "There's just something about a Windfree" that tickles your innards and with just Rudder and Elevator... who knew? lol
Ironically she's built for thermals and good luck out climbing a Windfree in a thermal: 2 lbs? lol
She hunts thermals well too: she's got decent legs and doesn't lose much altitude going from one dying thermal to another developed one. She's light on the winch and gets incredible launch altitude
If you find one in good condition or better yet still in the box, don't pass it up! Don't build her heavy in defense of her daintiness "that's not her game"! I enlarge her rudder for slope soaring and I shorten the hole in the elevator horn by 1/8th of an inch or so for a-bit more elevator throws but that's the only changes from the plans. (The rudder horn is fine, it's not that long and the rudder is enlarged)
2lbs 1/4oz, all up which is crazy light for a 99" span Sailplane. 8ft 3"
Wing area 560sq inches which is crazy few for a 99" sailplane. Most 72" spans have more.
Aspect ratio 17.15 to 1 (there are many ways to calculate this, I can't remember which way I chose)
Airfoil: flat bottom, 10% thick
When you double the aspect ratio you halve the induced drag (her extreme light weight further reduces induced drag) and the remaining forms of drag are very reduced in sailplanes. Thin fuselage's reduce profile drag, thin airfoils reduce intersection drag, reduced surface area reduces skin drag, Windfrees' elevator is full flying and is therefore small and it has a symmetrical airfoil with an inner spar, her vertical stabilizer is very thin, her wings have enough sheeting that there is little monocote sag in the rib bays
Monocote rib bay sag: In-Short:
High aspect ratio wings inherently have short chord lengths which in turn produces stall at lessor angle of attacks. Upper wing airflows at the leading edge and to some distance back are always a laminar airflow. In having the sheeting end at a particular location (beginning the sag) trips the airflow into a turbulent airflow which in turn increases the possible angle before stall occurs and virtually "fixes" the high aspect ratio wings pre-mature stall problem and in creating only slightly more drag. In making the bays minimal so as to trip the airflow "just/only enough" to get the job done and in using the correct size cap strips whose surface area doesn't trip the airflow but in designing for the correct lateral spread of said turbulent airflow to eventually coalesce to create a turbulent airflow across the entire wingspan requires a specific rib bay and cap strip sizing.
The Windfree designer Mark Smith knew his sh*t!
Windfrees' fuselage is larger than many, but it really doesn't cost her much in drag because she's not traveling at composite Sailplane speeds. There are no ailerons or flaps or spoilers "control surface gaps" nor does she carry the extra mechanical weight of having and operating them.
She has her own unique game and remains competitive still today!
Out of all my Sailplanes if I could only keep 2 it'd be both of my Windfrees!
There's a-lot of special somethings about a Windfree!
Cheers
Robert
10 авг 2022
